Your example is incomplete as you don't say what string you would need to run it against for it to produce pathological behaviour.

As I've mentioned, I've produced many that take a long time to process, but I'm failing to grasp the significance of what aspects take time, and which consume stack. Maybe this should be obvious to me, but it isn't.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.